Set Up Improvement of Impedance Spectroscopy Characterization of Chitosan Membranes

摘要

An Electrochemical Impedance Spectroscopy (EIS) technique was used to measure electrical properties of membranes as a function of frequency. A small signal of AC potential was applied to a charged chitosan membrane with amplitude of 2V over a frequency range of 100–300 kHz. An experimental set up was improved by adjusting two measuring electrodes from vertical to horizontal direction to the membrane plane, and being closer to the membrane surface. The test membrane was made from 400K MW chitosan with 78 % DDA. Electrical properties of the membrane were investigated by immersing the membrane in KCl solution. The results showed that the impedance obtained from vertical and horizontal direction was 17.2 kΩ and 1.3 kΩ, respectively, in 0.1 mM salt concentration. When the salt concentration was reduced by ten fold to 0.01 mM, the measured value for the former and the latter was 30.1 kΩ and 4.5 kΩ, respectively. After this improvement, the conductance and capacitance of membranes were also greater by 90 % approximately. Moreover, the membranes exhibited much greater diffusion potential and ionic permeability ratios.